This invention relates to integrated circuits and, more particularly, to integrated circuit comparators.
A comparator is a circuit that compares the instantaneous magnitude of a first input signal to the magnitude of a second input signal. If the magnitude of the first input signal is less than the magnitude of the second input signal, then the comparator generates an output signal having a first logic level. If the magnitude of the first input signal is greater than the magnitude of the second input signal, then the comparator generates an output signal having a second logic level.
An ideal comparator has infinite gain and infinite bandwidth. A comparator having infinite gain and infinite bandwidth can convert a small analog signal to a large logic signal very quickly. Unfortunately, most comparators are not ideal. The gain of most high-bandwidth comparators is usually low, less than about ten, and the bandwidth of most high-gain comparators is also low, less than about one megahertz. For some comparator applications, such as detecting a light level change in a smoke detector, the gain-bandwidth product is not critical to the success of the application. A comparator having a gain of about ten and a bandwidth of about one megahertz is suitable for use in connection with a smoke detector. However, there is a great demand for comparators that can operate in high-speed signaling applications that are common in modem digital systems, such as microprocessors, digital signal processors, communications circuits, and storage systems. These high-speed signaling applications require the comparator gain to be as high as possible, usually much greater than ten, and the comparator bandwidth also to be as high as possible, usually much greater than one megahertz.
For these an other reasons there is a need for a comparator having a high gain-bandwidth product.